This invention relates to a technique of processing data in a computer system, and more particularly, to a technique applicable to database management systems that have a system-switching function (failover function).
In any data base management system (hereinafter abbreviated as DBMS), localization of the effect of a failure and quick recovery of the system from the failure are important in order to improve the reliability of the system and raise the operating rate of the system. A technology that has conventionally been employed in DBMSs for quick system recovery from a failure is “system switching (failover)” in which a standby node is prepared separately from an active node, which executes services, and execution of the services is turned over to the standby system when a failure occurs in the active system.
A known countermeasure against DBMS failures is a technique of giving a system a hot standby configuration, so that the system can be run non-stop (see , for example, Jim Gray and Andreas Reuter, “Transaction Processing: Concepts and Techniques”, pp. 646-648, 925-927, Morgan Kaufmann Publishers, 1992).
There has also been known an architecture in which a plurality of processors execute database processing to balance the database processing load among the processors. An example of this architecture is disclosed in David DeWitt and Jim Gray, “Parallel Database Processing: The Future of High Performance Database Systems”, pp. 1-26, COMMUNICATIONS OF THE ACM, Vol. 35, N06, 1992. The publication discloses a shared-everything architecture as well as a shared-disk architecture (sharing architectures), and in this type of system, every disk is accessible to every node that performs DB processing. In a shared-nothing architecture (non-sharing architecture), each node can only access data stored in a disk that is connected to the node.
The above-mentioned prior art example discusses server pooling and the like in which one backup node is prepared for each active node, so that failover switching is made from an arbitrary node suffering a failure to a predetermined standby node. On the other hand, node addition and configuration change in terms of hardware have become easier due in part to the recent emergence of blade server, and software technology is now attracting attention which enables a DBMS to make full use of existing nodes in the system when a blade is added.